Black Death devastated Europe in the 14th century but scientists have now found the deadly bacteria has been around for thousands of years.

Yersinia pestis, the bacteria that causes plague, has been found in the remains of a 20-year-old Stone Age woman who died 4,900 years ago in Sweden.

Scientists now believe that farmers that lived 4,500 years ago may have also been killed by the ‘Black Death’ after it spread to the provinces from rapidly growing civilisations.

This is the oldest trace of the deadly bacteria ever found and scientists say it could rewrite the history of ancient Europeans.

They say the dawn of the Bronze Age and trading of excess goods may have facilitated the the spread of the plague to different regions and into Europe.

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This image shows the remains of a 20-year old woman from around 4,900 ago. She was likely killed by the first plague pandemic. She was one of the victims of a plague pandemic that likely lead to the decline of the Neolithic societies in Europe, scientists claim

Previously it was believed invaders from Asia brought plague with them but the new findings suggest a breakout occurred far before these colonists arrived.

A team of French, Swedish and Danish researchers identified a new strain of Yersinia pestis, the bacteria that causes plague.

Senior author Associate Professor Simon Rasmussen, at the Technical University of Denmark and the University of Copenhagen, explained: ‘Plague is maybe one of the deadliest bacteria that has ever existed for humans.

‘And if you think of the word ‘plague,’ it can mean this infection by Y. pestis, but because of the trauma plague has caused in our history, it’s also come to refer more generally to any epidemic.

‘The kind of analyses we do here let us go back through time and look at how this pathogen that’s had such a huge effect on us evolved.’

The evolution of the plague was mapped through genetic data from ancient humans, and sequencing modern plague strains.

Genes that make the pneumonic plague deadly were found in the Swedish remains.

Traces of it were also found in the remains of another person at the site and it is believed the woman did die from the disease.

By comparing it to other strains, the researchers were able to determine that it’s also the most basal, meaning that it’s the closest strain we have to the genetic origin of Y. pestis.

It likely diverged from other strains around 5,700 years ago and the plague that was common in the Bronze Age and the plague that is the ancestor of the strains in existence today diverged 5,300 and 5,100 years ago, respectively.

This suggests that there were multiple strains of plague in existence at the end of the Neolithic period, according to the researchers.

Professor Rasmussen added the finding offers a new theory about how plague spreads.

Massive human migrations from the Eurasian steppe down into Europe are known to have occurred around 5,000 years ago.

But how these cultures were able to displace the Neolithic farming culture present in Europe at the time is still debated.

Previous researchers suggested the invaders brought the plague with them, wiping out the large settlements of Stone Age farmers when they arrived.

The Black Death in the 1340s was one of the deadliest outbreaks of disease in human history. Pictured: a mass grave uncovered at the site of a 14th-century monastery in Lincolnshire

The strain of plague in the Swedish woman diverged from the rest of Y. pestis 5,700 years ago and likely evolved before migrations and when Neolithic European settlements were already starting to collapse.

Mega-settlements of up to 20,000 inhabitants were becoming common in Europe, which made job specialisation, new technology, and trade possible.

Professor Rasmussen explained: ‘These mega-settlements were the largest settlements in Europe at that time, ten times bigger than anything else.

‘That’s the textbook example of what you need to evolve new pathogens. We think our data fit.

‘If plague evolved in the mega-settlements, then when people started dying from it, the settlements would have been abandoned and destroyed.

‘This is exactly what was observed in these settlements after 5,500 years ago.

‘Plague would also have started migrating along all the trade routes made possible by wheeled transport, which had rapidly expanded throughout Europe in this period.’

The plague then spread out from big settlements to smaller communities where the woman was found.

Researchers have not yet identified the plague in individuals from the mega-settlements where it may have evolved.

WHAT CAUSED EUROPE’S BUBONIC PLAGUES?

The plague, caused by the bacterium Yersinia pestis, was the cause of some of the world’s deadliest pandemics, including the Justinian Plague, the Black Death, and the major epidemics that swept through China in the late 1800s.

The disease continues to affect populations around the world today.

The Black Death of 1348 famously killed half of the people in London within 18 months, with bodies piled five-deep in mass graves.

When the Great Plague of 1665 hit, a fifth of people in London died, with victims shut in their homes and a red cross painted on the door with the words ‘Lord have mercy upon us’.

The pandemic spread from Europe through the 14th and 19th centuries – thought to come from fleas which fed on infected rats before biting humans and passing the bacteria to them.

But modern experts challenge the dominant view that rats caused the incurable disease.

Experts point out that rats were not that common in northern Europe, which was hit equally hard by plague as the rest of Europe, and that the plague spread faster than humans might have been exposed to their fleas.

Most people would have had their own fleas and lice, when the plague arrived in Europe in 1346, because they bathed much less often.